Runner complaining about runner limit met without queued jobs

I have a gitlab-runner instance set up for autoscaling with docker+machine and DigitalOcean. I'm seeing a lot of this spammed in my log, despite there being no queued jobs:

Mar 06 03:22:40 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:40 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:43 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:43 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:46 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:46 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:49 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:49 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:52 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d
Mar 06 03:22:52 gitlab-runner-master gitlab-runner[1152]: ERROR: Failed to process runner                     builds=0 error=failed to request job, runner limit met executor=docker+machine runner=abc-d

My configuration for this is as follows:

concurrent = 2

[[runners]]
  name = "gitlab-runner-master"
  url = "https://gitlab.com/"
  token = "redacted"
  executor = "docker+machine"
  limit = 1
  [runners.docker]
    image = "alpine:latest"
  [runners.machine]
    IdleCount = 0
    IdleTime = 3600
    MachineName = "gitlab-runner-autoscale-%s"
    MachineDriver = "digitalocean"
    MachineOptions = [
        "digitalocean-image=coreos-stable",
        "digitalocean-ssh-user=core", 
        "digitalocean-access-token=redacted", 
        "digitalocean-region=sfo2", 
        "digitalocean-size=1gb", 
        "digitalocean-private-networking" 
    ]
  [runners.cache]
    Type = "s3"
    ServerAddress = "sfo.spaces.digitaloceanspaces.com"
    AccessKey = "redacted"
    SecretKey = "redacted"
    BucketName = "redacted"
    Insecure = false

Am I missing something?